WASHINGTON — A large-scale naval exercise by Iran last week in the Strait of Hormuz was a designed message to the United States, Army Gen. Joseph Votel said Wednesday.

The U.S. Central Command chief told reporters at the Pentagon that the exercise was a reaction to new sanctions imposed by President Donald Trump’s administration against the Iranians, who wanted to demonstrate they were capable of shutting down the strait, which is a major oil transport route because it is the only water passage from the Persian Gulf to the ocean.

“I think it’s pretty clear to us that they were trying to use that exercise to send a message to us that as we approach the period of the sanctions here that they have some capabilities,” he said.

The exercise included about 100 Iranian vessels primarily from its elite Revolutionary Guard Corps and occurred much earlier in the year than such Iranian maritime operations have in past years, said Votel, who oversees American operations in the Middle East and southwest Asia. However, the scope and scale of the exercise were not unusual, he said.

Moreover, Votel said there were no unsafe or unprofessional interactions between the Iranians and American warships during the exercise, continuing a roughly year-long pattern of professional interactions between the two sides.

The operation did catch Americans’ attention, Votel said.

Among their key operations in and around the Persian Gulf and the Arabian Sea, which are connected by the Strait of Hormuz, the U.S. military aims to ensure freedom of navigation and the flow of commerce in international waters. Some 18 million barrels of oil move through the strait each day, making it one of the world’s most busy chokepoints.

Iran’s president Hassan Rouhani has threatened to shut down the strait in response to sanctions re-imposed on the Iranian regime this week by Trump, who in May withdrew from a 2015 agreement easing sanctions on Iran in exchange for restrictions on its nuclear programs.

Asked Wednesday if the Iranians were capable of closing the strait, Votel declined to answer. Instead, he said the Iranian navy had extensive military abilities that could be problematic for the area. He listed mines, explosive boats and coastal defense missiles as capabilities that would create concern if Iran attempted to shut down the waterway and forced the United States to respond.

“I’d certainly suggest that we have capabilities as well,” the general said. “We routinely focus on de-mining exercises in the region and we maintain forces and readiness … in the region that are well-trained and well-prepared to deal with these types of situations.”

Votel said the U.S. military in the region continues closely monitoring Iran’s activities, but he stopped short of saying the United States has adjusted its posture in the region in response to the exercise and rhetoric from Iranian leaders. Rouhani, for example, called the renewed sanctions by Trump “psychological warfare.”

Despite the increased tensions, Votel said the Iranians’ continued professional actions in waterways near its country that in recent years saw dozens of precarious interactions, including incidents that resulted in warning shots being fired.

The U.S. Navy has reported zero unsafe or unprofessional interactions with the Iranian military since August 2017. That follows 14 incidents earlier in 2017, 36 in 2016 and 22 in 2015. Votel has seen such unsafe interactions firsthand. In July 2016, he was aboard the USS New Orleans, a San Antonio-class amphibious transport dock, cruising the Strait of Hormuz when Iranian boats approached quickly in an “aggressive manner.”

The general said he has come up with no explanation why those aggressive actions — the vast majority carried out by Iranian Revolutionary Guard swift boats – have ceased.

“I’m glad that’s the case,” Votel said. “I would encourage them to continue to do that. We expect our maritime forces to operate in a professional manner, and I think we should expect that from others who operate in the international maritime environment.”